Semiconductor device structure and methods of forming the same

ABSTRACT

An interfacial structure, along with methods of forming such, are described. The structure includes a first interfacial layer having a first dielectric layer, a first conductive feature disposed in the first dielectric layer, and a first thermal conductive layer disposed on the first dielectric layer. The structure further includes a second interfacial layer disposed on the first interfacial layer. The second interfacial layer is a mirror image of the first interfacial layer with respect to an interface between the first interfacial layer and the second interfacial layer. The second interfacial layer includes a second thermal conductive layer disposed on the first thermal conductive layer, a second dielectric layer disposed on the second thermal conductive layer, and a second conductive feature disposed in the second dielectric layer.

BACKGROUND

The semiconductor industry has experienced rapid growth due tocontinuous improvements in the integration density of various electroniccomponents (i.e., transistors, diodes, resistors, capacitors, etc.). Forthe most part, this improvement in integration density has come fromrepeated reductions in minimum feature size, which allows morecomponents to be integrated into a given area.

These integration improvements are essentially two-dimensional (2D) innature, in that the volume occupied by the integrated components isessentially on the surface of a substrate, such as the semiconductorwafer. Although dramatic improvement in lithography has resulted inconsiderable improvement in 2D integrated circuit (IC) formation, thereare physical limits to the density that may be achieved in twodimensions. One of these limits is the minimum size needed to make thesecomponents. In addition, when more devices are put into one chip or die,more complex designs are required.

In an attempt to further increase circuit density, three-dimensionalintegrated circuits (3DICs) have been investigated. In a typicalformation process of a 3DIC, two chips or substrates are bondedtogether. However, performance and reliability of 3DICs may benegatively impacted at high temperature. For example, conventionalintermetal dielectric (IMD) material such as SiO₂ may not meet thethermal management demand from substrate stacking due to the lowintrinsic thermal conductivity. Therefore, there is a need to solve theabove problems.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1A is a perspective view of one of various stages of manufacturinga semiconductor device structure, in accordance with some embodiments.

FIG. 1B is a cross-sectional side view of the stage of manufacturing thesemiconductor device structure taken along line A-A of FIG. 1A, inaccordance with some embodiments.

FIG. 2 is a cross-sectional side view of a stage of manufacturing thesemiconductor device structure, in accordance with some embodiments.

FIGS. 3A-3E are cross-sectional side views of various stages ofmanufacturing the semiconductor device structure, in accordance withsome embodiments.

FIGS. 4A-4D are cross-sectional side views of various stages ofmanufacturing the semiconductor device structure, in accordance withalternative embodiments.

FIGS. 5A-5E are cross-sectional side views of various stages ofmanufacturing the semiconductor device structure, in accordance withalternative embodiments.

FIGS. 6A-6E are cross-sectional side views of various stages ofmanufacturing the semiconductor device structure, in accordance withalternative embodiments.

FIGS. 7A-7C are cross-sectional side views of various stages ofmanufacturing the semiconductor device structure, in accordance withalternative embodiments.

FIGS. 8A-8D are cross-sectional side views of various stages ofmanufacturing the semiconductor device structure, in accordance withalternative embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “over,” “on,” “top,” “upper” and the like, may be used hereinfor ease of description to describe one element or feature'srelationship to another element(s) or feature(s) as illustrated in thefigures. The spatially relative terms are intended to encompassdifferent orientations of the device in use or operation in addition tothe orientation depicted in the figures. The apparatus may be otherwiseoriented (rotated 90 degrees or at other orientations) and the spatiallyrelative descriptors used herein may likewise be interpretedaccordingly.

FIGS. 1A and 1B illustrate a stage of manufacturing a semiconductordevice structure 100. As shown in FIGS. 1A and 1B, the semiconductordevice structure 100 includes a substrate 102 having substrate portions104 extending therefrom and source/drain (S/D) epitaxial features 106disposed over the substrate portions 104. The substrate 102 may be asemiconductor substrate, such as a bulk silicon substrate. In someembodiments, the substrate 102 may be an elementary semiconductor, suchas silicon or germanium in a crystalline structure; a compoundsemiconductor, such as silicon germanium, silicon carbide, galliumarsenic, gallium phosphide, indium phosphide, indium arsenide, and/orindium antimonide; other suitable materials; or combinations thereof.Possible substrates 102 also include a silicon-on-insulator (SOI)substrate. SOI substrates are fabricated using separation byimplantation of oxygen (SIMOX), wafer bonding, and/or other suitablemethods. The substrate portions 104 may be formed by recessing portionsof the substrate 102. Thus, the substrate portions 104 may include thesame material as the substrate 102. The substrate 102 and the substrateportions 104 may include various regions that have been suitably dopedwith impurities (e.g., p-type or n-type impurities). The dopants are,for example boron for a p-type field effect transistor (PFET) andphosphorus for an n-type field effect transistor (NFET). The S/Depitaxial features 106 may include a semiconductor material, such as Sior Ge, a III-V compound semiconductor, a II-VI compound semiconductor,or other suitable semiconductor material. Exemplary S/D epitaxialfeatures 106 may include, but are not limited to, Ge, SiGe, GaAs,AlGaAs, GaAsP, SiP, InAs, AlAs, InP, GaN, InGaAs, InAlAs, GaSb, AlP,GaP, and the like. The S/D epitaxial features 106 may include p-typedopants, such as boron; n-type dopants, such as phosphorus or arsenic;and/or other suitable dopants including combinations thereof.

An insulating material 108 is disposed between adjacent substrateportions 104, as shown in FIG. 1A. The insulating material 108 may bemade of an oxygen-containing material, such as silicon oxide orfluorine-doped silicate glass (FSG); a nitrogen-containing material,such as silicon nitride, silicon oxynitride (SiON), SiOCN, SiCN; a low-kdielectric material (e.g., a material having a k value lower than 7); orany suitable dielectric material. The insulating material 108 may be theshallow trench isolation (STI). Dielectric features 110 may be formedover the insulating material 108 to separate adjacent S/D epitaxialfeatures 106. The dielectric feature 110 may include a single dielectricmaterial, such as the dielectric material of the insulating material108, or different dielectric materials. As shown in FIG. 1A, thedielectric feature 110 includes a first dielectric material 112, a liner114, and a second dielectric material 116. The liner 114 may include alow-k dielectric material, such as SiO₂, SiN, SiCN, SiOC, or SiOCN. Thefirst dielectric material 112 may include an oxygen-containing material,such as an oxide, and may be formed by FCVD. The oxygen-containingmaterial may have a K value less than about 7, for example less thanabout 3. In some embodiments, the first dielectric material 112 includesthe same material as the insulating material 108. The second dielectricmaterial 116 may include SiO, SiN, SiC, SiCN, SiON, SiOCN, AlO, AN,AlON, ZrO, ZrN, ZrAlO, HfO, or other suitable dielectric material. Insome embodiments, the second dielectric material 116 includes a high-kdielectric material (e.g., a material having a k value greater than 7).

A contact etch stop layer (CESL) 118 and an interlayer dielectric (ILD)layer 120 are disposed over the dielectric features 110, as shown inFIG. 1A. The CESL 118 may include an oxygen-containing material or anitrogen-containing material, such as silicon nitride, silicon carbonnitride, silicon oxynitride, carbon nitride, silicon oxide, siliconcarbon oxide, the like, or a combination thereof. The materials for theILD layer 120 may include tetraethylorthosilicate (TEOS) oxide, un-dopedsilicate glass, or doped silicon oxide such as borophosphosilicate glass(BPSG), fused silica glass (FSG), phosphosilicate glass (PSG), borondoped silicon glass (BSG), and/or other suitable dielectric materials. Acap layer 122 may be disposed on the ILD layer 120, and the cap layer122 may include a nitrogen-containing material, such as SiCN.

Conductive contacts 126 may be disposed in the ILD layer 120 and overthe S/D epitaxial features 106, as shown in FIGS. 1A and 1B. Theconductive contacts 126 may include one or more electrically conductivematerial, such as Ru, Mo, Co, Ni. W, Ti, Ta, Cu, Al, TiN and TaN.Silicide layers 124 may be disposed between the conductive contacts 126and the S/D epitaxial features 106.

As shown in FIG. 1B, S/D epitaxial features 106 may be connected by oneor more semiconductor layers 130, which may be channels of a FET. Insome embodiments, the FET is a nanosheet FET including a plurality ofsemiconductor layers 130, and at least a portion of each semiconductorlayer 130 is wrapped around by a gate electrode layer 136. Thesemiconductor layer 130 may be or include materials such as Si, Ge, SiC,GeAs, GaP, InP, InAs, InSb, GaAsP, AlInAs, AlGaAs, InGaAs, GaInP,GaInAsP, or other suitable material. In some embodiments, eachsemiconductor layer 130 is made of Si. The gate electrode layer 136includes one or more layers of electrically conductive material, such aspolysilicon, aluminum, copper, titanium, tantalum, tungsten, cobalt,molybdenum, tantalum nitride, nickel silicide, cobalt silicide, TiN, WN,WCN, TiAl, TiTaN, TiAlN, TaN, TaCN, TaC, TaSiN, metal alloys, othersuitable materials, and/or combinations thereof. In some embodiments,the gate electrode layer 136 includes a metal. A gate dielectric layer134 may be disposed between the gate electrode layer 136 and thesemiconductor layers 130. The gate dielectric layer 134 may include twoor more layers, such as an interfacial layer and a high-k dielectriclayer. In some embodiments, the interfacial layer is an oxide layer, andthe high-k dielectric layer includes hafnium oxide (HfO₂), hafniumsilicate (HfSiO), hafnium silicon oxynitride (HfSiON), hafnium aluminumoxide (HfAlO), hafnium lanthanum oxide (HfLaO), hafnium zirconium oxide(HfZrO), hafnium tantalum oxide (HMO), hafnium titanium oxide (HfTiO),lanthanum oxide (LaO), aluminum oxide (AlO), aluminum silicon oxide(AlSiO), zirconium oxide (ZrO), titanium oxide (TiO), tantalum oxide(Ta₂O₅), yttrium oxide (Y₂O₃), silicon oxynitride (SiON), hafniumdioxide-alumina (HfO₂—Al₂O₃) alloy, or other suitable high-k materials.The gate dielectric layer 134 and the gate electrode layer 136 may beseparated from the S/D epitaxial features 106 by inner spacers 132. Theinner spacers 132 may include a dielectric material, such as SiON, SiCN,SiOC, SiOCN, or SiN. The gate dielectric layer 134 and the gateelectrode layer 136 may be separated from the CESL 118 by spacers 128.The spacers 128 may include a dielectric material such as silicon oxide,silicon nitride, silicon carbide, silicon oxynitride, SiCN, siliconoxycarbide, SiOCN, and/or combinations thereof. In some embodiments, aself-aligned contact (SAC) layer 140 is formed over the spacers 128, thegate dielectric layer 134, and the gate electrode layer 136, as shown inFIGS. 1A and 1B. The SAC layer 140 may include any suitable materialsuch as SiO, SiN, SiC, SiON, SiOC, SiCN, SiOCN, AlO, AlON, ZrO, ZrN, orcombinations thereof.

As shown in FIGS. 1A and 1B, the semiconductor device structure 100 mayinclude the substrate 102 and a device layer 200 disposed over thesubstrate 102. The device layer 200 may include one or more devices,such as transistors, diodes, imaging sensors, resistors, capacitors,inductors, memory cells, combinations thereof, and/or other suitabledevices. In some embodiments, the device layer 200 includes transistors,such as nanosheet FET having a plurality of channels wrapped around bythe gate electrode layer, as described above. The term nanosheet is usedherein to designate any material portion with nanoscale, or evenmicroscale dimensions, and having an elongate shape, regardless of thecross-sectional shape of this portion. Thus, this term designates bothcircular and substantially circular cross-section elongate materialportions, and beam or bar-shaped material portions including for examplea cylindrical in shape or substantially rectangular cross-section. Thenanosheet channel(s) of the semiconductor device structure 100 may besurrounded by the gate electrode layer. The nanosheet transistors may bereferred to as nanowire transistors, gate-all-around (GAA) transistors,multi-bridge channel (MBC) transistors, or any transistors having thegate electrode layer surrounding the channels. In some embodiments, thedevice layer 200 includes planar FET, FinFET, complementary FET (CFET),forksheet FET, or other suitable devices.

The semiconductor device structure 100 may further includes aninterconnection structure 300 disposed over the device layer 200 and thesubstrate 102, as shown in FIG. 2. The interconnection structure 300includes various conductive features, such as a first plurality ofconductive features 304 and second plurality of conductive features 306,and an intermetal dielectric (IMD) layer 302 to separate and isolatevarious conductive features 304, 306. In some embodiments, the firstplurality of conductive features 304 are conductive lines and the secondplurality of conductive features 306 are conductive vias. Theinterconnection structure 300 includes multiple levels of the conductivefeatures 304, and the conductive features 304 are arranged in each levelto provide electrical paths to various devices in the device layer 200disposed below. The conductive features 306 provide vertical electricalrouting from the device layer 200 to the conductive features 304 andbetween conductive features 304. For example, the bottom-most conductivefeatures 306 of the interconnection structure 300 may be electricallyconnected to the conductive contacts 126 (FIG. 1B) and the gateelectrode layer 136 (FIG. 1B). The conductive features 304 andconductive features 306 may be made from one or more electricallyconductive materials, such as metal, metal alloy, metal nitride, orsilicide. For example, the conductive features 304 and the conductivefeatures 306 are made from copper, aluminum, aluminum copper alloy,titanium, titanium nitride, tantalum, tantalum nitride, titanium siliconnitride, zirconium, gold, silver, cobalt, nickel, tungsten, tungstennitride, tungsten silicon nitride, platinum, chromium, molybdenum,hafnium, other suitable conductive material, or a combination thereof.

The IMD layer 302 includes one or more dielectric materials to provideisolation functions to various conductive features 304, 306. The IMDlayer 302 may include multiple dielectric layers embedding multiplelevels of conductive features 304, 306. The IMD layer 302 is made from adielectric material, such as SiO_(x), SiO_(x)C_(y)H_(z), orSiO_(x)C_(y), where x, y and z are integers or non-integers. In someembodiments, the IMD layer 302 includes a dielectric material having a kvalue ranging from about 1 to about 5. The material of the IMD layer 302has a low thermal conductivity, such as less than about 1.5 Watts permeter-Kelvin (W/m*K), for example from about 1.2 W/m*K to about 1.5W/m*K.

As shown in FIG. 3A, a structure 400 is formed on a structure 401. Thestructure 401 may be the semiconductor device structure 100 shown inFIG. 2. For example, the structure 400 is formed on the interconnectstructure 300 (FIG. 2). In some embodiments, the structure 401 may bethe semiconductor device structure 100 shown in FIG. 1B, and thestructure 400 is formed on the device layer 200 (FIG. 1B). In someembodiments, the substrate 102 (FIG. 1B and FIG. 2) may be a wafer, suchas a 200 mm, 300 mm, 450 mm, or other suitable sized wafer. In suchembodiments, the structure 401 includes devices, such as devices formedin the device layer 200 (FIG. 1B), formed on the wafer. Thus, astructure 350 shown in FIG. 3A may be a wafer having materials formedthereon. In some embodiments, the structure 401 may be a die havingdevices, such as the devices formed in the device layer 200 (FIG. 1B),formed on the substrate 102, which is cut from a wafer. Thus, thestructure 350 shown in FIG. 3A may be a die having materials formedthereon.

As shown in FIG. 3A, the structure 400 may be formed by first forming adielectric layer 402 over the structure 401 and them forming openings404 (only one is shown) in the dielectric layer 402. One or more etchstop layers (not shown) may be formed between the dielectric layer 402and the structure 401. The openings 404 may expose portions of thestructure 401. In some embodiments, the top-most conductive features 304(FIG. 2) in the interconnect structure 300 (FIG. 2) are exposed by theopenings 404. In some embodiments, the conductive contacts 126 (FIG. 1B)and the gate electrode layer 136 (FIG. 1B) may be exposed by theopenings 404. The dielectric layer 402 may include the same material asthe IMD layer 302 and may be formed by chemical vapor deposition (CVD),atomic layer deposition (ALD), spin coating, or other suitable process.In some embodiments, an anneal or UV cure process may be performed afterdepositing the dielectric layer 402. The openings 404 may be formed byany suitable process, such as dry etch, wet etch, or a combinationthereof.

As shown in FIG. 3B, a barrier layer 406 and a conductive feature 408are formed in each opening 404. The barrier layer 406 may include Co, W,Ru, Al, Mo, Ti, TiN, TiSi, CoSi, NiSi, Cu, TaN, Ni, or TiSiNi and may beformed by any suitable process, such as physical vapor deposition (PVD),ALD, or plasma-enhanced CVD (PECVD). In some embodiments, the barrierlayer 406 may be a conformal layer formed by a conformal process, suchas ALD. The term “conformal” may be used herein for ease of descriptionupon a layer having substantial same thickness over various regions. Theconductive feature 408 may include an electrically conductive material,such as a metal. For example, the conductive feature 408 includes Cu,Ni, Co, Ru, Jr, Al, Pt, Pd, Au, Ag, Os, W, Mo, alloys thereof, or othersuitable material. The conductive feature 408 may be formed by anysuitable process, such as electro-chemical plating (ECP), PVD, CVD, orPECVD. A planarization process is performed to remove the portions ofthe barrier layer 406 and the conductive feature 408 disposed on thedielectric layer 402, as shown in FIG. 3B. The planarization process maybe any suitable process, such as a chemical-mechanical polishing (CMP)process.

As shown in FIG. 3C, a thermal conductive layer 410 is formed on thedielectric layer 402. In some embodiments, the dielectric layer 402 maybe recessed, and the thermal conductive layer 410 may include a surface412 that is substantially co-planar with a surface 414 of the conductivefeature 408. For example, the dielectric layer 402 is recessed by aselective etch process that removes a portion of the dielectric layer402 but not the barrier layer 406 or the conductive feature 408. Thethermal conductive layer 410 is then formed on the recessed dielectriclayer 402 by a suitable process, such as ALD, CVD, or spin coating. Thethermal conductive layer 410 may be initially formed on the dielectriclayer 402, the barrier layer 406, and the conductive feature 408, and aplanarization process may be performed to expose the barrier layer 406and the conductive feature 408. The planarization process may be anysuitable process, such as CMP process, that removes portions of thethermal conductive layer 410 formed on the barrier layer 406 and theconductive feature 408. The thermal conductive layer 410 may have athickness ranging from about 1 nm to about 5000 nm.

The thermal conductive layer 410 may include a material having thermalconductivity higher than that of the dielectric layer 402. In someembodiments, the thermal conductive layer 410 includes a material havingthermal conductivity greater than about 1.5 W/m*K, such as from about 2W/m*K to about 2500 W/m*K. The thermal conductive layer 410 may includea material such as SiC, SiN, SiCN, AlN, AlO, boron nitride (BN),diamond, diamond-like carbon (DLC), graphene oxide, graphite, or othersuitable material. In some embodiments, the thermal conductive layer 410includes BN, DLC, graphene oxide, or graphite. The material of thethermal conductive layer 410 may be monocrystalline or polycrystalline.

The structure 350 shown in FIG. 3C may be a wafer having materialsformed thereon or an IC die, as described above. In some embodiments, inorder to form a 3DIC, the structure 350 shown in FIG. 3C may be bondedto another structure. As shown in FIG. 3D, the structure 350 is bondedto a structure 350′. The structure 350′ may be a wafer having devicesformed thereon or an IC die, depending on the nature of the structure350. In some embodiments, a wafer-stacking process includes bonding afirst wafer having materials formed thereon to a second wafer havingmaterials formed thereon, and the first and second wafers may be thestructures 350, 350′, respectively. In some embodiments, the twostructures 350, 350′ may be bonded by hybrid bonding at a temperatureranging from about 20 degrees Celsius to about 400 degrees Celsius. As aresult of bonding the two structures 350, 350′, a plurality of 3DICs areformed, each 3DIC includes first devices in the structure 350electrically coupled to second devices in the structure 350′.Subsequently, a wafer dicing process may be performed on the bondedstructures 350, 350′ to form a plurality of separated 3DICs.

In some embodiments, a die-stacking process includes bonding a first dieto a second die, and the first and second dies may be the structures350, 350′, respectively. The bonding of the dies may be the same as thebonding of wafers, as described above. As a result, a 3DIC die isformed.

As shown in FIG. 3D, the structure 350′ is bonded to the structure 350.The structure 350′ may include a structure 400′ disposed over astructure 401′. The structure 400′ may include the same materials as thestructure 400. For example, the structure 400′ may include a dielectriclayer 402′, barrier layers 406′, conductive features 408′, and a thermalconductive layer 410′. The dielectric layer 402′ may include the samematerial as the dielectric layer 402, the barrier layers 406′ mayinclude the same material as the barrier layers 406, the conductivefeatures 408′ may include the same material as the conductive features408, and the thermal conductive layer 410′ may include the same materialas the thermal conductive layer 410. The arrangement of the barrierlayers 406′, the conductive features 408′, and the thermal conductivelayer 410′ may be the same as the arrangement of the barrier layers 406,the conductive features 408, and the thermal conductive layer 410. Insome embodiments, the structure 400′ is identical to the structure 400.

In some embodiments, the structure 401′ is identical to the structure401. In some embodiments, the structure 401′ is different from thestructure 401. For example, the structure 401′ may include the substrate102 (FIG. 1B), the device layer 200 (FIG. 1B), and optionally theinterconnect structure 300 (FIG. 2). The device layer 200 in thestructure 401′ may be different from the device layer 200 in thestructure 401. The interconnect structure 300 in the structure 401′ maybe different from the interconnect structure 300 in the structure 401.The differences in the device layers 200 in the structure 401′ comparedto in the structure 401 may be the type of devices, the number ofdevices, or the arrangement of devices.

As shown in FIG. 3D, the structure 350′ may be flipped over and bondedto the structure 350, and the structure 400 is bonded to the structure400′. For example, the thermal conductive layer 410 is bonded to thethermal conductive layer 410′, and the conductive feature 408 is bondedto the conductive feature 408′. The bonding may be a result of exposingthe structures 350′, 350 to a temperature ranging from about 20 degreesCelsius to about 400 degrees Celsius. The thermal management capabilityfor wafer stacking or die stacking may be improved due to increasedthermal conductivity of the thermal conductive layers 410, 410′ comparedto the thermal conductivity of the dielectric layers 402, 402′.Furthermore, bondable thermal conductive layers 410, 410′ may improvethermal dissipation and more efficient bonding process. Thus, if thethickness of the thermal conductive layer 410 is less than about 1 nm,the thermal conductive layer 410 may not be sufficient to improvethermal management capability for wafer stacking or die stacking and/orto improve thermal dissipation. On the other hand, if the thickness ofthe thermal conductive layer 410 is greater than about 5000 nm,manufacturing cost is increased without significant advantage.

The bonded structures 400, 400′ form an interfacial structure 420, asshown in FIG. 3D. In some embodiments, the interfacial structure 420includes the structures 400, 400′ that are substantially symmetricalwith respect to an interface between the structures 400, 400′. Forexample, the conductive feature 408 may include a tapered sidewall 409,the corresponding conductive feature 408′ disposed over the conductivefeature 408 may include a corresponding tapered sidewall 409′ disposedover the tapered sidewall 409, and the tapered sidewall 409 and thetapered sidewall 409′ may taper in opposite directions. Because thestructures 400, 400′ are substantially symmetrical, the conductivefeatures 408 are aligned with corresponding conductive features 408′. Insome embodiments, the structure 400′ is a mirror image of the structure400 with respect to an interface between the structure 400 and thestructure 400′.

As shown in FIG. 3E, in some embodiments, the structures 400, 400′ aresubstantially asymmetrical, and the conductive features 408 may beslightly misaligned but still in contact with corresponding conductivefeatures 408′. For example, the barrier layer 406 may be in contact withthe conductive feature 408′ and the thermal conductive layer 410′, andthe barrier layer 406′ may be in contact with the conductive feature 408and the thermal conductive layer 410. In some embodiments, the thermalconductive layer 410′ may be disposed over the barrier layer 406 and aportion of the conductive feature 408. The conductive feature 408′ maybe disposed over the barrier layer 406 and a portion of the thermalconductive layer 410.

FIGS. 4A-4D illustrate an alternate method of forming the structure 400and the structure 400′. As shown in FIG. 4A, the conductive features 408are formed over the structure 401. The conductive features 408 may beformed by first forming a conductive layer over the structure 401followed by patterning the conductive layer to form the conductivefeatures 408. Openings 403 are formed as a result of the patterning theconductive layer.

As shown in FIG. 4B, the barrier layers 406 and the dielectric layers402 are formed in the openings 403. In some embodiments, the dielectriclayers 402 may be initially formed in the openings 403 and on theconductive features 408, and a subsequent planarization process may beperformed to expose the conductive features 408. As a result, surfacesof the dielectric layers 402 may be co-planar with surfaces of theconductive features 408, as shown in FIG. 4B. As shown in FIG. 4C, thedielectric layers 402 may be recessed, and the thermal conductive layer410 may be formed on the dielectric layers 402. The thermal conductivelayer 410 may include the surface 412 that is substantially co-planarwith the surface 414 of the conductive feature 408. In some embodiments,the dielectric layers 402 are formed to the level shown in FIG. 4C, andthe planarization and recess processes may be omitted. As shown in FIG.4C, the structure 400 is formed over the structure 401.

As shown in FIG. 4D, the structure 350′ may include the structure 400′which may be identical to the structure 400 and the structure 401′ whichmay or may not be identical to the structure 401, as described in FIG.3D. The structure 350′ may be flipped over and bonded to the structure350, and the structure 400 is bonded to the structure 400′. For example,the thermal conductive layer 410 is bonded to the thermal conductivelayer 410′, and the conductive feature 408 is bonded to the conductivefeature 408′. The bonding may be a result of exposing the structures350′, 350 to a temperature ranging from about 20 degrees Celsius toabout 400 degrees Celsius. The thermal management capability for waferstacking or die stacking may be improved due to increased thermalconductivity of the thermal conductive layers 410, 410′ compared to thethermal conductivity of the dielectric layers 402, 402′. Furthermore,bondable thermal conductive layers 410, 410′ may improve thermaldissipation and more efficient bonding process.

The bonded structures 400, 400′ form the interfacial structure 420, asshown in FIG. 4D. In some embodiments, the interfacial structure 420includes the structures 400, 400′ that are substantially symmetricalwith respect to an interface between the structures 400, 400′. Becausethe structures 400, 400′ are substantially symmetrical, the conductivefeatures 408 are aligned with corresponding conductive features 408′. Insome embodiments, the structures 400, 400′ are substantiallyasymmetrical, and the conductive features 408 may be slightly misalignedbut still in contact with corresponding conductive features 408′.

FIGS. 5A-5E illustrate a method of forming a structure 500 and astructure 500′. For example, the structures 500, 500′ may be formed by adual-damascene process. As shown in FIG. 5A, a structure 550 includesthe structure 500, which may be formed by first forming a firstdielectric layer 502 and a second dielectric layer 506 over the firstdielectric layer 502. The first dielectric layer 502 and the seconddielectric layer 506 may be separated by an etch stop layer 504. One ormore etch stop layers (not shown) may be formed between the firstdielectric layer 502 and the structure 401. The first and seconddielectric layers 502, 506 may include the same material as thedielectric layer 402 and may be formed by the same method as thedielectric layer 402. The etch stop layer 504 may include anoxygen-containing material or a nitrogen-containing material, such assilicon nitride, silicon carbon nitride, silicon oxynitride, carbonnitride, silicon oxide, silicon carbon oxide, the like, or a combinationthereof. The etch stop layer 504 may be formed by CVD, PECVD, ALD, orany suitable deposition technique. In some embodiments, the etch stoplayer 504 is a conformal layer formed by the ALD process. The etch stoplayer 504 and the first and second dielectric layers 502, 506 may havedifferent etch selectivity. Openings 508 may be formed in the seconddielectric layer 506 to expose portions of the etch stop layer 504. Insome embodiments, openings 508 are trenches.

As shown in FIG. 5B, a portion of the exposed portions of the etch stoplayer 504 and a portion of the first dielectric layer 502 disposedtherebelow are removed to expose portions of the structure 401. Openings510 are formed as a result of the removal of the portions of the etchstop layer 504 and the first dielectric layer 502. In some embodiments,the top-most conductive features 304 (FIG. 2) in the interconnectstructure 300 (FIG. 2) are exposed by the openings 510. In someembodiments, the conductive contacts 126 (FIG. 1B) and the gateelectrode layer 136 (FIG. 1B) may be exposed by the openings 510. Theopenings 510 may have smaller dimensions than the openings 508. In someembodiments, the openings 510 are via openings.

As shown in FIG. 5C, a barrier layer 512 and a conductive feature 514are formed in each opening 508, 510. The barrier layer 512 may includethe same material as the barrier layer 406, and the conductive feature514 may include the same material as the conductive feature 408. Thebarrier layer 512 may be formed by the same method as the barrier layer406, and the conductive feature 514 may be formed by the same method asthe conductive feature 408. In some embodiments, the conductive feature514 includes a via portion in the first dielectric layer 502 and a lineportion in the second dielectric layer 506. As shown in FIG. 5D, thesecond dielectric layer 506 may be recessed and a thermal conductivelayer 516 is formed on the recessed second dielectric layer 506. Thethermal conductive layer 516 may include the same material as thethermal conductive layer 410 and may be formed by the same method as thethermal conductive layer 410. The recessing of the second dielectriclayer 506 may be by the same method as the recessing of the dielectriclayer 402 described in FIG. 3C. In some embodiments, the thermalconductive layer 516 may include a surface 518 that is substantiallyco-planar with a surface 519 of the conductive feature 514.

As shown in FIG. 5E, a structure 550′ is bonded to the structure 550.The structure 550′ may include the structure 500′ disposed over thestructure 401′. The structure 500′ may include the same materials as thestructure 500. For example, the structure 500′ may include a firstdielectric layer 502′, an etch stop layer 504′, a second dielectriclayer 506′, barrier layers 512′, conductive features 514′, and a thermalconductive layer 516′. The first and second dielectric layers 502′, 506′may include the same materials as the first and second dielectric layers502, 506, respectively, the etch stop layer 504′ may include the samematerial as the etch stop layer 504, the barrier layers 512′ may includethe same material as the barrier layers 512, the conductive features514′ may include the same material as the conductive features 514, andthe thermal conductive layer 516′ may include the same material as thethermal conductive layer 516. The arrangement of the barrier layers512′, the conductive features 514′, and the thermal conductive layer516′ may be the same as the arrangement of the barrier layers 512, theconductive features 514, and the thermal conductive layer 516. In someembodiments, the structure 500′ is identical to the structure 500. Thestructure 401′ may or may not be identical to the structure 401, asdescribed in FIG. 3D.

As shown in FIG. 5E, the structure 550′ may be flipped over and bondedto the structure 550, and the structure 500 is bonded to the structure500′. For example, the thermal conductive layer 516 is bonded to thethermal conductive layer 516′, and the conductive feature 514 is bondedto the conductive feature 514′. The bonding may be a result of exposingthe structures 550′, 550 to a temperature ranging from about 20 degreesCelsius to about 400 degrees Celsius. The thermal management capabilityfor wafer stacking or die stacking may be improved due to increasedthermal conductivity of the thermal conductive layers 516, 516′ comparedto the thermal conductivity of the dielectric layers 502, 502′, 506,506′. Furthermore, bondable thermal conductive layers 516, 516′ mayimprove thermal dissipation and more efficient bonding process.

The bonded structures 500, 500′ form an interfacial structure 520, asshown in FIG. 5E. In some embodiments, the interfacial structure 520includes the structures 500, 500′ that are substantially symmetricalwith respect to an interface between the structures 500, 500′. Becausethe structures 500, 500′ are substantially symmetrical, the conductivefeatures 514 are aligned with corresponding conductive features 514′. Insome embodiments, the structures 500, 500′ are substantiallyasymmetrical, and the conductive features 514 may be slightly misalignedbut still in contact with corresponding conductive features 514′.

FIGS. 6A-6E illustrate an alternate method of forming the structure 400and the structure 400′. As shown in FIGS. 6A and 6B, which is similar toFIGS. 3A and 3B, the dielectric layer 402 is formed over the structure401, and the barrier layers 406 and the conductive features 408 areformed in the openings 404 in the dielectric layer 402. As shown in FIG.6C, a cap layer 602 is selectively formed on each conductive feature408. The cap layer 602 may include one or more layers of two-dimensional(2D) material, such as graphene. For example, graphene may only grow onthe conductive surface of the conductive feature 408 but not thedielectric surface of the dielectric layer 402. The cap layer 602 may bealso formed on the barrier layers 406. In some embodiments, the numberof 2D material layers ranges from about 3 to about 17000, and thethickness of the cap layer 602 may range from about 1 nm to about 5000nm. For example, the cap layer 602 includes 3 to 17000 layers ofgraphene and have a thickness ranging from about 1 nm to about 5000 nm.The thermal conductive layer 410 may be selectively formed on thedielectric surface of the dielectric layer 402 and not on the cap layer602. For example, the cap layer 602 includes one or more layers ofgraphene, which prevents the thermal conductive layer 410 from grownthereon. In some embodiments, a small amount, such as a negligibleamount, of the thermal conductive layer 410 may be formed on the caplayer 602. In some embodiments, the cap layer 602 may have the samethickness as the thermal conductive layer 410. In some examples, thesurface 412 of the thermal conductive layer 410 may be substantiallyco-planar with a surface 604 of the cap layer 602.

As shown in FIG. 6D, the structure 350′ is bonded to the structure 350.The structure 350′ may include the structure 400′ disposed over thestructure 401′. The structure 400′ may include the same materials as thestructure 400. A cap layer 602′ may include the same material and samenumber of layers of 2D material as the cap layer 602. In someembodiments, the structure 400′ is identical to the structure 400. Thestructure 350′ may be flipped over and bonded to the structure 350, andthe structure 400 is bonded to the structure 400′. For example, thethermal conductive layer 410 is bonded to the thermal conductive layer410′, and the cap layer 602 is bonded to the cap layer 602′. In additionto the benefits of having the thermal conductive layers 410, 410′, thecap layers 602, 602′ can function as electromigration barrier layers andcan lower electrical resistance. Thus, if the thickness of the cap layer602 is less than about 1 nm, the cap layer 602 may not be sufficient tolower electrical resistance and/or to function as an electromigrationlayer. On the other hand, if the thickness of the cap layer 602 isgreater than about 5000 nm, manufacturing cost is increased withoutsignificant advantage.

The bonded structures 400, 400′ form an interfacial structure 420, asshown in FIG. 6D. In some embodiments, the interfacial structure 420includes the structures 400, 400′ that are substantially symmetricalwith respect to an interface between the structures 400, 400′. Becausethe structures 400, 400′ are substantially symmetrical, the cap layer602 is aligned with corresponding cap layer 602′.

As shown in FIG. 6E, in some embodiments, the structures 400, 400′ aresubstantially asymmetrical, and the cap layer 602 may be slightlymisaligned but still in contact with corresponding cap layer 602′. Forexample, the thermal conductive layer 410 may be in contact with aportion of the cap layer 602′, and the thermal conductive layer 410′ maybe in contact with a portion of the cap layer 602. In some embodiments,the thermal conductive layer 410′ is disposed over a portion of the caplayer 602, and the cap layer 602′ is disposed over a portion of thethermal conductive layer 410.

FIGS. 7A-7C illustrate an alternate method of forming the structure 400and the structure 400′. As shown in FIG. 7A, the structure 400 is formedon a structure 401. The structure 400 may be formed by first forming athermal conductive layer 702 over the structure 401 and them forming theopenings 404 (only one is shown) in the thermal conductive layer 702.One or more etch stop layers (not shown) may be formed between thethermal conductive layer 702 and the structure 401. The openings 404 mayexpose portions of the structure 401. In some embodiments, the top-mostconductive features 304 (FIG. 2) in the interconnect structure 300 (FIG.2) are exposed by the openings 404. In some embodiments, the conductivecontacts 126 (FIG. 1B) and the gate electrode layer 136 (FIG. 1B) may beexposed by the openings 404. The thermal conductive layer 702 mayinclude the same material as the thermal conductive layer 410 (FIG. 3C)and may be formed by CVD, ALD, spin coating, or other suitable process.The thermal conductive layer 702 may be deposited at a temperature lessthan about 425 degrees Celsius. In some embodiments, an anneal or UVcure process may be performed after depositing the thermal conductivelayer 702. The openings 404 may be formed by any suitable process, suchas dry etch, wet etch, or a combination thereof. The barrier layer 406and the conductive feature 408 are formed in each opening 404, as shownin FIG. 7B.

The thermal conductive layer 702, the barrier layers 406, and theconductive features 408 may be formed by the process flow described inFIGS. 4A and 4B. For example, in some embodiments, the conductivefeatures 408 are formed first, followed by forming the barrier layers406 and the thermal conductive layer 702. In some embodiments, thethermal conductive layer 702, the barrier layers 406, and the conductivefeatures 408 may be formed by a dual-damascene process as described inFIGS. 5A-5D. For example, the first and second dielectric layers 502,506 described in FIGS. 5A-5D may be replaced with the first and secondthermal conductive layers.

As shown in FIG. 7C, the structure 350′ is bonded to the structure 350.The structure 350′ may include the structure 400′ disposed over thestructure 401′. The structure 400′ may include the same materials as thestructure 400. For example, the structure 400′ includes a thermalconductive layer 702′, and barrier layers 406′ and conductive features408′ are formed in the thermal conductive layer 702′. In someembodiments, the structure 400′ is identical to the structure 400. Thestructure 350′ may be flipped over and bonded to the structure 350, andthe structure 400 is bonded to the structure 400′. For example, thethermal conductive layer 702 is bonded to the thermal conductive layer702′, and the conductive features 408 are bonded to the conductivefeatures 408′. The thermal management capability for wafer stacking ordie stacking may be improved due to increased thermal conductivity ofthe thermal conductive layers 702, 702′. Furthermore, bondable thermalconductive layers 702, 702′ may improve thermal dissipation and moreefficient bonding process.

The bonded structures 400, 400′ form the interfacial structure 420, asshown in FIG. 7C. In some embodiments, the interfacial structure 420includes the structures 400, 400′ that are substantially symmetricalwith respect to an interface between the structures 400, 400′. Becausethe structures 400, 400′ are substantially symmetrical, the conductivefeatures 408 are aligned with corresponding conductive features 408′. Insome embodiments, the structures 400, 400′ are substantiallyasymmetrical, and the conductive features 408 may be slightly misalignedbut still in contact with corresponding conductive features 408′.

FIGS. 8A-8D illustrate an alternate method of forming the structure 400and the structure 400′. As shown in FIGS. 8A and 8B, which is similar toFIGS. 7A and 7B, the thermal conductive layer 702 is formed over thestructure 401, and the barrier layers 406 and the conductive features408 are formed in the openings 404 in the thermal conductive layer 702.As shown in FIG. 8C, the cap layer 602 is selectively formed on eachconductive feature 408. The cap layer 602 may be also formed on thebarrier layers 406. In some embodiments, the conductive features 408 andthe barrier layers 406 may be recessed before selectively forming thecap layer 602 on each conductive feature 408.

As shown in FIG. 8D, the structure 350′ is bonded to the structure 350.The structure 350′ may include the structure 400′ disposed over thestructure 401′. The structure 400′ may include the same materials as thestructure 400. For example, the structure 400′ includes the thermalconductive layer 702′, the cap layer 602′, the barrier layers 406′, andconductive features 408′. The cap layer 602′ may include the samematerial and same number of layers of 2D material as the cap layer 602.In some embodiments, the structure 400′ is identical to the structure400. The structure 350′ may be flipped over and bonded to the structure350, and the structure 400 is bonded to the structure 400′. For example,the thermal conductive layer 702 is bonded to the thermal conductivelayer 702′, and the cap layer 602 is bonded to the cap layer 602′.

The bonded structures 400, 400′ form an interfacial structure 420, asshown in FIG. 8D. In some embodiments, the interfacial structure 420includes the structures 400, 400′ that are substantially symmetricalwith respect to an interface between the structures 400, 400′. Becausethe structures 400, 400′ are substantially symmetrical, the cap layer602 is aligned with corresponding cap layer 602′. In some embodiments,the structures 400, 400′ are substantially asymmetrical, and the caplayer 602 may be slightly misaligned but still in contact withcorresponding cap layer 602′.

The present disclosure in various embodiments provides a thermalconductive layer in a 3DIC and the method of making the 3DIC. Thethermal conductive layers may be disposed in the interfacial structureas a result of bonding two structures. In some embodiments, the thermalconductive layer may be formed over a dielectric material havingconductive features formed therein. In some embodiments, the conductivefeatures are formed in the thermal conductive layer. The presentdisclosure further provides a cap layer formed on the conductivefeatures. Some embodiments may achieve advantages. For example, thethermal management capability for wafer stacking or die stacking may beimproved due to increased thermal conductivity of the thermal conductivelayers, which also may improve thermal dissipation and more efficientbonding process. Furthermore, the cap layer can function aselectromigration barrier layers and can lower electrical resistance.

An embodiment is an interfacial structure. The structure includes afirst structure having a first dielectric layer, a first conductivefeature disposed in the first dielectric layer, and a first thermalconductive layer disposed on the first dielectric layer. The firstconductive feature includes a first sidewall. The structure furtherincludes a second structure disposed on the first structure. The secondstructure includes a second thermal conductive layer disposed on thefirst thermal conductive layer, a second dielectric layer disposed onthe second thermal conductive layer, and a second conductive featuredisposed in the second dielectric layer. The second conductive featurehas a second sidewall disposed over the first sidewall, and the firstsidewall and the second sidewall taper in opposite directions.

Another embodiment is an interfacial structure. The structure includes afirst structure having a first thermal conductive layer and a firstconductive feature disposed in the first thermal conductive layer. Thefirst thermal conductive layer includes SiC, SiN, SiCN, AlN, AlO_(x),BN, diamond, diamond-like carbon, graphene oxide, or graphite. Thestructure further includes a second structure disposed on the firststructure. The first structure and the second structure aresubstantially symmetrical with respect to an interface between the firststructure and the second structure. The second structure includes asecond thermal conductive layer disposed on the first thermal conductivelayer and a second conductive feature disposed in the second thermalconductive layer.

A further embodiment is a 3DIC. The 3DIC includes a first device layerand a first structure disposed over the first device layer. The firststructure includes a first dielectric layer, a first conductive featuredisposed in the first dielectric layer, and a first thermal conductivelayer disposed on the first dielectric layer. The first thermalconductive layer has a higher thermal conductivity than the firstdielectric layer. The 3DIC further includes a second structure disposedon the first structure. The second structure includes a second thermalconductive layer disposed over a portion of the first thermal conductivelayer and a portion of the first conductive layer, a second dielectriclayer disposed on the second thermal conductive layer, and a secondconductive feature disposed in the second dielectric layer. The secondconductive feature is disposed over a portion of the first conductivefeature and a portion of the first thermal conductive layer. The 3DICfurther includes a second device layer disposed over the secondstructure.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

1. An interfacial structure, comprising: a first structure, comprising:a first dielectric layer; a first conductive feature disposed in thefirst dielectric layer, wherein the first conductive feature has a firstsidewall; a first cap layer disposed on the first conductive feature;and a first thermal conductive layer disposed on the first dielectriclayer; and a second structure disposed on the first structure, whereinthe second structure comprises: a second thermal conductive layerdisposed on the first thermal conductive layer; a second dielectriclayer disposed on the second thermal conductive layer; a secondconductive feature disposed in the second dielectric layer, wherein thesecond conductive feature has a second sidewall disposed over the firstsidewall, and the first sidewall and the second sidewall taper inopposite directions; and a second cap layer disposed between the secondconductive feature and the first cap layer.
 2. The interfacial structureof claim 1, wherein the first and second thermal conductive layers eachcomprises SiC, SiN, SiCN, AlN, AlO_(x), BN, diamond, diamond-likecarbon, graphene oxide, or graphite.
 3. The interfacial structure ofclaim 2, wherein the first and second dielectric layers each comprisesSiO_(x), SiO_(x)C_(y)H_(z), or SiO_(x)C_(y).
 4. The interfacialstructure of claim 1, wherein the first structure further comprises afirst barrier layer disposed in the first dielectric layer, wherein thefirst barrier layer is in contact with the first conductive feature. 5.The interfacial structure of claim 4, wherein the second structurefurther comprises a second barrier layer disposed in the seconddielectric layer, wherein the second barrier layer is in contact withthe second conductive feature.
 6. The interfacial structure of claim 1,wherein the first and second cap layers each comprises one or morelayers of a two-dimensional material.
 7. The interfacial structure ofclaim 1, wherein the first thermal conductive layer comprises a firstsurface, the first cap layer comprises a second surface, and the firstand second surfaces are substantially co-planar. 8-13. (canceled)
 14. Athree-dimensional integrated circuit, comprising: a first device layer;a first structure disposed over the first device layer, wherein thefirst interfacial layer comprises: a first dielectric layer; a firstconductive feature disposed in the first dielectric layer; a first caplayer disposed on the first conductive feature; and a first thermalconductive layer disposed on the first dielectric layer, wherein thefirst thermal conductive layer has a higher thermal conductivity thanthe first dielectric layer; a second structure disposed on the firststructure, wherein the second structure comprises: a second thermalconductive layer disposed over a portion of the first thermal conductivelayer; a second dielectric layer disposed on the second thermalconductive layer; a second conductive feature disposed in the seconddielectric layer, wherein the second conductive feature is disposed overa portion of the first conductive feature and a portion of the firstthermal conductive layer; and a second cap layer disposed between thesecond conductive feature and the first cap layer; and a second devicelayer disposed over the second structure.
 15. The three-dimensionalintegrated circuit of claim 14, further comprising: a first interconnectstructure disposed between the first device layer and the firststructure; and a second interconnect structure disposed between thesecond device layer and the second structure.
 16. The three-dimensionalintegrated circuit of claim 15, wherein the first device layer comprisesfirst one or more devices, and the second device layer comprises secondone or more devices.
 17. The three-dimensional integrated circuit ofclaim 16, wherein the first and second one or more devices each compriseone or more transistors.
 18. The three-dimensional integrated circuit ofclaim 17, wherein the one or more transistors are nanosheet transistors.19. The three-dimensional integrated circuit of claim 16, wherein thefirst and second interconnect structures each comprises a plurality ofconductive features disposed in a dielectric material.
 20. Thethree-dimensional integrated circuit of claim 19, wherein the first andsecond cap layers each comprises one or more layers of a two-dimensionalmaterial.
 21. A method for forming an interfacial structure, comprising:forming a first structure, comprising: forming an opening in adielectric layer; forming a conductive feature in the opening;selectively forming a first cap layer on the conductive feature; andforming a first thermal conductive layer on the dielectric layer,wherein a surface of the first thermal conductive layer and a surface ofthe first cap layer are substantially co-planar; and forming a secondstructure; and bonding the second structure to the first structure. 22.The method of claim 21, wherein the second structure comprises a secondcap layer and a second thermal conductive layer.
 23. The method of claim22, wherein the first thermal conductive layer is bonded to the secondthermal conductive layer, and the first cap layer is bonded to thesecond cap layer.
 24. The method of claim 21, wherein the first caplayer comprises one or more layers of a two-dimensional material. 25.The method of claim 24, wherein the two-dimensional material comprisesgraphene.
 26. The method of claim 21, wherein the first thermalconductive layer is selectively formed on the dielectric layer.